Alarm system



'Jun'e 10, 1930. l I H. A. FREDERICK I 1,762,973

ALARM SYSTEM Filed April 28, 1926 `Pai:ended .June 10, i939 HALSEX'` AUGUSTUS FREDERICK, OF MOUNTAIN LAKES, NEW JERSEY, ASSIGNORTO i'" BELL TELEPHONE LABORATORIES, INCORPORATED,

-POR-TATION OF NEW-YORK `f 'lfhis inventionrelates to alarm systems, fand more particularly to .systems for the protection of vaults, and the like, from burglary., f, .A l.1 v A l arg' i An object of the invention'i's to enable tlie'dete'ction of vibrations, or other' disturbances in a vault or other structure. p

' Another object ofthe invention is to enable a distinction to be made, in the detec- 10 tion of vibrations, between vibrations set up in the structure itself and vibrations set up "in the air adjacentto the structure.

l The practice heretofore followed in alarm systems for vaults and the like, was to em- 15v ploy a sound detector such as a sensitive telephone transmitter which -was located in'` or about the vault to be protected, and was responsive to sound waves in the air, emanating from disturbances in or about the vault. This type of transmitter was also responsive Ato vibrations received from all directions and produced by disturbances around the. outside :of the building in whiclrthe vault was lo` cated, thereby rendering the alarm systems of this character susceptible to Vmany false alarms. ,y d y According to the present invention a more .highly eiiicient and reliable alarm system is attainable by employing a" detector, preferably of the inertiainicrophone type, so ar ranged vthat the vibration responsive elementrthereof is secured to the wall or shell of the vault, or other structure to be protected. By this method it follows that a direct and more dependable coupling is secured between the alarm system and the disturbance, which latter may be caused by any instrument such :is a hammer, drill, chisel, torch or the like, used to force an entrance into the protected structure. The microphone here employed i is designed to respond only to those vibrations having frequencies within a particular range as produced in the protected structure by someone tampering with the walls thereof. 'produced by disturbances other than Vthose in the walls of the structure, may be made practically ineffective to actuate the microphone since such an instrument may be made non-responsive to sound waves in the air.

kALARM -ss'rnlvr Application ined, april 2s,

In this arrangement it has xalsobeen found,

In this way sound waves or vibrations OF NEW YORK, N. Y., A. COR- issis. seriarnouioaose.

by several testsp'and experiments,` that the microphone is practically'nonresponsive to vibrations produced` by passing subway trains, trucks and the like, andfthatffal'se "5g alarms which are registered in systems heretofore due to the tendency' of the'microphones thereinto flutter or move in response to vibrations at right angles to their axes, have been entirely eliminated. The manner 'en in which this has been-effected will be heie inafter described.` A Y f f 4 A The invention further contemplates the use of a relay tuned to respond to electric f currents set up by the vibrations detected by 65 the microphone. This relay is preferably tuned to respond to a definite `band of fre:- quencies of vibrations and to respond less 'sensitively to vibrations of other frequencies.

The relay in operating, renders effectivev an Z0 alarm to give notice that the structure is being molested. Y The above and other objects and advantages of this invention are set forth in the following description and appended'claims 75 vand may be more readily understood if considered in `conjunction with `the accompany;

ing drawing illustratingthe invention, in which l* ig. l shows a complete system ac cording to this invention ttorl operating an so alarm device at a distant point in response to the vibrations produced by disturbances in the vault or similar structures, Fig. 2 shows a. different form of alarm signal applied to v the system shown in Fig. l, and Fig. 3 shows 85 a modified form of the system of Fig. ll in which amplifying' means ,may be employed for operating `a loud speaking device at the distant point. ,A f z: Referring now to Fig. l of the drawing', 30 the protective system'consists oa` seriesof circuits comprising a local circuit which in# cludes a highly sensitive transmitter 2, mounted on the interior portion of wall l of transmitter that may be adapted forvuse in this invention is disclosed in PatentNo.

1,4%,7 57 granted to C. R. Moore on August j 22, 1922. The Moore type microphone is 100 bracket or a reed which may of itself be either mounted on the Wall or suspended from the ceilingl and be tuned to the frequency band of greatest int-crest and which may be so designed as to match the highimpedance of the Wall With the lower impedance of the transmitter button.

What is claimed is:

1'. In a protective system for vaults, the

combination with avertical Wall thereof of an electric ,circuitincluding a vibration detector mounted on the Wall, and having' its contacts adapted to be operated only by mechanical vibrations substantially perpendicular to the Wall and Within the frequency range to which the Wall readily responds, a relay tuned to respond only to current variations of the frequencies produced by said detector, and alarm means controlled by the operation of said relay.

2. In a protective system for vaults, the combination with a vertical wall thereof of an electric circuit including,` a vibration responsive device havingcontacts and alarm means responsive to the operation of the contacts, the device being` mounted on the wall and having its contacts adapted to be opened only by vibrations substantially perpendicular to the Wall and Within the frequency range to which the Wall readily re sponds.

3. In a protective system for vaults, the combination with a vertical Wall thereof of an electric circuit including a vibration responsive device having;` contacts, a circuit closing relay responsive to the operation of the contacts and an alarm responsive to the operation of the circuit closing device, the device being mounted on the Wall and having 4o its contacts adapted to be opened only by vibrations substantially perpendicular to the Wall and Wit-hin the frequency range to Which the Wall readily responds.

In Witness whereof, I hereunto subscribe my name this 2'? day of April A. D. 1926.

HALSEY A. FREDERICK. 

